The determination of the proper refractive corrections to obtain maximized vision is normally accomplished utilizing a graded series of lenses which are held in the viewer's line of vision. The patient is asked to relate whether each successive lens produces an improvement or deterioration of the image of a target. Cylindrical correction is similarly obtained by the process of manually rotating the axis of the cylindrical correction through increments until 180.degree. of possible orientation have been experimented with. Proper cylindrical power is then obtained by applying a graded series of cylindrical powers to obtain maximum visual accuity. The determination of the relative power for spherical and cylindrical corrections is always a difficult judgement decision. This and the other judgement decisions associated with a vision examination are compounded when the patient is too young or otherwise unable to adequately express the difference between successive lenses. In view of the many judgement decisions involved throughout the process, it is not possible to delegate the task of refraction to non-professional personnel, and therefore the task is normally carried out by the optometrist or ophthalmologist himself. This results in a relatively inefficient vision examination process and increases the cost of the process.
The deficiencies in the prior art technique for vision examinations have resulted in the development of a number of proposed vision examination aids. Apparatus that detect the angulation of a laser beam, or similar light beam, passed into the eye and reflected from the retina have been developed and marketed. These and other idirect methods have the disadvantage that they are limited to the optical characteristics of the mechanical eyeball itself and do not take into effect the optic nerve and brain functions which produce the total vision system of an individual. Further, the possible eye damage due to excessive power levels in the laser beam and overall complexity of these units has limited the scope of their application.
Therefore it is desirable to have a vision examination apparatus and lens system that facilitates the examination of the human eye from the standpoint of prescribing refractive lenses to the point where portions of the examination can be conducted by non-professional personnel, and wherein the examination includes the total vision system including the brain and optic nerve.